This invention relates generally to rotary machines and more particularly, to a lubrication heating system for operating wind turbines in cold weather environments.
Generally, a wind turbine includes a rotor having multiple blades. The blades are attached to a rotatable hub, and the blades and hub are often called the rotor. The rotor transforms mechanical wind energy into a mechanical rotational torque that drives one or more generators. The generators are generally, but not always, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the turbine rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid. Gearless direct drive wind turbine generators also exist. The rotor, generator, gearbox and other components are typically mounted within a housing, or nacelle, that is positioned on top of a base that may be a truss or tubular tower.
The gearboxes need to be lubricated to function effectively. Typically, oils are used for lubrication in a gearbox, and the oil heats up during operation of the gearbox. A heat exchanger can be used to cool the oil, and a suction pipe typically exits the gearbox and feeds into a circulating pump. The circulating pump is used to force the oil through the heat exchanger, and the cooled oil is then directed back to the gearbox.
In extremely cold environments (e.g., less than about −10 degrees C.), the lubrication oil used in the gearbox can become very viscous or thick. This cold and viscous oil resists flow and the circulating pump can be damaged if run when the oil is very cold. In some known solutions an external heater and pump are connected to the oil sump of the gearbox. This oil sump heater takes a long time to heat up all the oil in the gearbox sump and requires a large amount of energy. The result is a long delay during cold weather operation, waiting for the oil to come up to a minimum temperature, until the wind turbine can begin producing power, as well as lower overall efficiency due to the large power drain imposed by the oil sump pump/heater.
Accordingly, a need exists in the art for a system that will quickly heat the oil entering a circulating pump used with a gearbox, and that does not require a large amount of power or time to operate.